Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
412 FXUS62 KCAE 181835 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 235 PM EDT Wed Sep 18 2024 .SYNOPSIS... An upper low over the area will move slowly east to the coast by early Thursday. A few showers or thunderstorms are possible Thursday mainly in the east Midlands closer to the upper low. Moisture is expected to decrease Friday. High pressure will build into the area from New England over the weekend into early next week with dry and seasonable temperatures expected. && .NEAR TERM /THROUGH TONIGHT/... Key Message(s): - Scattered showers and a few thunderstorms into this evening. An upper level low continues to spin over the region this afternoon, with the center now over the SC upstate. Areas across the Midlands toward the coast are seeing some breaks in the clouds, with temperatures in the low to mid 80s. This has led to MLCAPE values between 500 and 1000 J/kg mainly east of the I-20 corridor. Upper level shortwave is helping to support isolated to scattered convection developing, though the best thermodynamics are south and east of our forecast area. CAM solutions are in good agreement that showers and storms are most likely closer to the coastal plain over the next few hours with precip diminishing after sunset as the low shifts east toward the coast. The threat of severe weather remains low given the weak instability and lack of shear. MOS guidance suggests we may have the redevelopment of some stratus or patchy fog tonight as skies clear from west to east. Lows overnight in the mid to upper 60s, though cooler temperatures are expected toward the upstate and warmer values toward the coast. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Key Message(s): - Isolated to scattered showers Thursday mainly in the east Midlands, drier Friday. - Seasonable temperatures. Thursday and Thursday night...Upper low will move into eastern North Carolina Thursday with long wave trough axis along the coast moving east in the morning. Moisture remains relatively high in the east Midlands with precipitable water near 1.75 inches. Models show a short wave trough moving through the area in the afternoon with the strongest lift focused closer to the Coastal Plain. Expect stronger diabatic heating than today across the region. Latest model forecast soundings for Thursday afternoon suggests moderate instability in the east Midlands with surface based CAPE around 1000-1500 J/kg. Weaker instability to the west due to lower moisture. Mid level subsidence inversion stronger in the west. So, a few light showers in the morning, then widely scattered/scattered showers mainly in the eastern area during the afternoon as moisture axis/short wave trough rotate through the area. Temperatures in the low to mid 80s. Convection should diminish in the early evening. Friday and Friday night...Low-level moisture remains high through the day especially in the east. Precipitable water only decreases slightly. There appears to be a weak cold front/moisture boundary moving south from eastern North Carolina in the afternoon. Latest GFS/Nam suggest a few showers may develop in the east again as another short wave moves through upper trough, but appears more focused in the Coastal Plain potentially aided by sea breeze convergence. The NBM pops are quite low and mean CAPE lower than Thursday. Any convection should be isolated. Temperatures a little warmer than Thursday. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Key Message(s): -Drier into early next week with warming trend over the weekend The ensembles continue to be in good agreement. Upper trough off the east coast with upper ridge over the southern Plains building east but flattening with time. Surface high ridging down the Eastern Seaboard. Low-level moisture remains high, high level moisture may increase by early Monday as the ridge flattens. Ensemble qpf probabilities > 0.1 inch only 10-20 % Sunday/Monday. NBM pops very low at this time so will continue dry forecast. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... Scattered showers and a few thunderstorms today may briefly reduce VSBYs at the terminals. MVFR CIGS possible Thursday morning. An upper level system will linger over the region today promoting scattered -SHRA/-TSRA and low clouds. Convection is expected to increase in coverage and intensity over the next several hours, though confidence is low regarding impacts at the terminals, particularly regarding any threat for thunder. Winds generally SLY/SWLY this afternoon at 5-10 kts. Later this evening into tonight, there is potential for another round MVFR/IFR CIG/VSBY restrictions at all terminals, though CAE/CUB are favored slightly more. Winds on Thursday generally becoming north to northeast behind the departing upper level system with skies clearing late in the day from west to east. EXTENDED AVIATION OUTLOOK...Drier air late this week should limit the threat of restrictions. As moisture begins to increase late this weekend and early next week we could see additional restrictions develop. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$